The main purpose of the work was to modify the surface layer of copper using FSP technology (Friction Stir Processing). The surface treatment was performed using a tool equipped with a threaded pin. Changes in the microstructure of the material were evaluated by light microscopy and scanning electron microscopy. Comparative measurement of the hardness of the starting and treated material was also carried out. It was found that the friction modification leads to strong refinement of the copper microstructure and the formation of zones with different sizes and morphology of the grains. In the stirring zone, the presence of very fine, mostly equiaxed grains, measuring from 3 μm to 32 μm, depending on the location in the zone, were revealed. In the narrow thermomechanically affected zone that intermeshed with the heat affected zone, non-equiaxed grains of an elongated shape prevailed. The observed changes in the copper microstructure were accompanied by a significant increase in hardness, the value of which corresponded to the degree of microstructure fragmentation. The results of the research prove that using FSP technology to modify the surface layer of copper is an effective and promising solution with a high application potential, allowing controlled shaping of the material microstructure and an alternative solution to other methods and technologies used in surface engineering.Keywords: Friction stir processing, copper, microstructure
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